There is currently intense interest in the chemistry of the vanadium oxide phosphate system because the system is capable of providing networks of connected vanadium and phosphorus polyhedra with a diversity of structures. This structural diversity is associated in part with the ability of vanadium oxygen coordination polyhedra to adopt tetrahedral, square pyramidal and octahedral geometries and to aggregate into larger cores by condensation of polyhedra through shared oxygen atoms. Further condensation with phosphate tetrahedra, such as PO.sub.4.sup.3-, HPO.sub.4.sup.2- and H.sub.2 PO.sub.4.sup.-1 results often in complex polyhedral networks.
Moreover, when cationic templates are introduced, polyhedral framework solids with tunnels, cages and micropores may be isolated. Such solids offer considerable promise since they make possible microporous framework solids, capable of shape selective absorption like the zeolites and aluminophosphates, that are useful as catalysts or molecular sieves.
Generally in the past with vanadium oxide phosphate systems, such templates have involved inorganic materials but the use of such materials has limited the size and shape of the micropores that can be realized. Of greater potential interest would be framework structures that could be assembled about templates of large size organic molecules that could later be removed, either by ion exchange or thermal methods, to leave pores of size comparable to those of the organic template molecules.
To this end, recently, hydrothermal self-assembly syntheses have been used to prepare microporous, octahedral framework molydenum phosphates formed about organic cationic templates, but these molydenum phosphate frameworks with organic cationic templates are of restricted applicability and there is interest in structures involving other metal phosphate compositions, such as vanadium phosphates, to increase the range of options.